In a conventional image pickup device, a first image is picked up for a standard exposure time. Thereafter, a second image is picked up by an image pickup unit for an exposure time shorter than the standard exposure time. A pixel reaching an upper limit value of the dynamic range with respect to a brightness value within this picked-up first image is replaced with a pixel within the above second image by a synthesizing unit so that the image of the wide dynamic range is generated.
In such an image pickup device, image data of each pixel of the first image are generally acquired by the synthesizing unit simultaneously with image data of the second image as a replacing candidate by delaying the image data of the first image by a buffer (e.g., see JP-A-2003-198948).
However, such an image pickup device requires a buffer having a large capacity for delaying the first image picked up for the standard exposure time. Further, the buffer capacity (delay time) depends on the construction of the image pickup unit. Further, when the delay time is changed in accordance with an image pickup condition, a complicated circuit that controls a change in the delay time is required. Therefore, there is a fear that the cost to manufacture the device is raised. Further, the exposure time is, conventionally, fixed at a period of one frame, and the synthesizing unit is constructed by using this fixed period. However, when the exposure time is dynamically changed, flexible coping is required in the synthesizing unit. Further, in an image pickup element having a plurality of channel outputs, each channel outputs a separate pixel series. Its construction therefore, becomes complicated when the exposure time is changed.
An object of the invention is to solve the above problems of the above conventional image pickup device, and to provide an image pickup device able at a reduced manufacture cost.